The drawback of using such possibility lists as described above is missing synonyms and other correct solutions in the user data and mislabeling them as Wrong. The edit distance is used to filter for such possible cases and then inspect and label this data by hand. The edit distance is a valuable tool, as most incorrect solutions include typos and wrong letters and are thus, by edit distance, very close to the correct set of solutions. We choose the Levenshtein distance [1]} as edit distance.
